<template>
  <div class="xtx-pagination">
<a href="javascript:;" v-if="myCurrentPage==1" class="disabled">上一页</a>
    <a href="javascript:;" v-else @click="go(-1)">上一页</a>

    <span v-if="pageInfo.start>2">...</span>
    <a
      href="javascript:;"
      :class="{active: myCurrentPage === item}"
      v-for="(item,idx) in pageInfo.pager"
      :key="idx"
      @click="changePage(item)">
    {{item}}
    </a>

    <span v-if="pageInfo.end < pageInfo.pageCount">...</span>

    <a href="javascript:;" v-if="myCurrentPage==pageInfo.end" class="disabled">下一页</a>
    <a href="javascript:;" v-else @click="go(1)">下一页</a>
  </div>
</template>
<script>
import { ref, computed, watch } from 'vue'
export default {
  name: 'XtxPagination',
  props: {
    total: { type: Number, default: 100 },
    pageSize: { type: Number, default: 10 },
    currentPage: { type: Number, default: 1 },
    btnCount: { type: Number, default: 5 }
  },
  setup (props, { emit }) {
    const myTotal = ref(100) // 总条数
    const myPageSize = ref(5) // 每页共几条

    const myCurrentPage = ref(2) // 用户实时点击，修改

    const myBtnCount = ref(5) // 分页按钮的个数5个

    watch(props, () => {
      myTotal.value = props.total
      myPageSize.value = props.pageSize
      myCurrentPage.value = props.currentPage
      myBtnCount.value = props.btnCount
    }, { immediate: true })
    // 根据上边信息，实时计算 pager，起始页码，结束页码
    const pageInfo = computed(() => {
      // 总页数
      const pageCount = Math.ceil(myTotal.value / myPageSize.value) // 一共有几页

      // 起始
      let start = myCurrentPage.value - Math.floor(myBtnCount.value / 2)
      // 结束
      let end = start + myBtnCount.value - 1

      // 意外1
      if (start < 1) {
        start = 1
        end = myBtnCount.value > pageCount ? pageCount : myBtnCount.value
      }

      // 意外2
      if (end > pageCount) {
        end = pageCount // 最大的页码
        start = (end - myBtnCount.value + 1) < 1 ? 1 : (end - myBtnCount.value + 1)
      }

      const pager = []
      for (let i = start; i <= end; i++) {
        pager.push(i)
      }

      return { pager, start, end, pageCount }
    })

    const changePage = (page) => {
      if (page === myCurrentPage.value) {
        return
      }

      myCurrentPage.value = page
      emit('current-change', page)
    }
    const go = step => {
      myCurrentPage.value = myCurrentPage.value + step
    }
    return { myTotal, myPageSize, myCurrentPage, myBtnCount, pageInfo, changePage, go }
  }
}
</script>
<style scoped lang="less">
.xtx-pagination {
  display: flex;
  justify-content: center;
  padding: 30px;
  > a {
    display: inline-block;
    padding: 5px 10px;
    border: 1px solid #e4e4e4;
    border-radius: 4px;
    margin-right: 10px;
    &:hover {
      color: @xtxColor;
    }
    &.active {
      background: @xtxColor;
      color: #fff;
      border-color: @xtxColor;
    }
    &.disabled {
      cursor: not-allowed;
      opacity: 0.4;
      &:hover {
        color: #333
      }
    }
  }
  > span {
    margin-right: 10px;
  }
}
</style>
